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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        var str = '123'
        var str_new = String(123) //构造函数

        var num = 100
        var num_new = Number('100')

        var bol = -true
        //转换布尔值，除了0等于false其他的值都是true
        //隐式转换
        var bol_new = Boolean(0)

        console.log(typeof str)
        console.log(typeof num)
        console.log(typeof bol)
    </script>
</body>

</html>